Herramientas

Calculators, drills, labs and printable sheets — 36 of them, sorted by what they are for. Every calculator works in imperial or metric (the switch at the top of the page), and any result can be kept: copy it, text it, share it, print it, or have the site email it to you. Where a number comes from the code — an ampacity, a fill limit, a derating factor — you type it from your own code book and the tool does the arithmetic.

Ejercicios

• 1st year

  Prueba de cinta métrica

  Read a tape to the nearest 1/16", timed or free practice.

• 1st year

  Fraction / decimal drill

  Fractions of an inch to decimals and back.

• 1st year

  Práctica de la ley de Ohm

  Solve for V, I, R or P at three levels, marked on the spot.

• 1st year

  Series / parallel practice

  Totals, string current and voltage drops across resistors.

• 1st year

  Conversion drill

  Inches ↔ millimetres, feet ↔ metres.

• 2nd year

  Offset math practice

  Distance between bends from the rise and angle.

• 2nd year

  Práctica de matemáticas del oficio

  Mixed practice and a printable 20-question worksheet.

Formulas & sheets

• 1st year

  Rueda de la ley de Ohm y la potencia

  Every rearrangement of V, I, R and P in one circle.

• 1st year

  Fraction / decimal / mm chart

  Sixteenths to decimals to millimetres, printable.

• 2nd year

  Multiplicadores de doblado y encogimiento

  Multiplier and shrink per angle, from the trigonometry.

• 3rd year

  Single & three phase formulas

  Power and current formulas on one page.

• 1st year

  Hoja de referencia de matemáticas del oficio

  Fractions, triangles, percent and area.

AC theory

• 2nd year

  Reactancia capacitiva e inductiva

  XL and XC at any frequency, the impedance with a resistance in series, and the resonant frequency.

• 2nd year

  Constante de tiempo RC / RL

  τ = RC or L/R, the five-time-constant table, and the percentage reached at any moment.

• 2nd year

  Triángulo de potencias y factor de potencia

  Volts, amps and power factor, single- or three-phase: kVA, kW, kVAR and the angle, drawn to scale.

Basic circuits

• 1st year

  Calculadora de ley de Ohm y potencia

  Type any two of volts, amps, ohms and watts; get the other two and the formula that did it.

• 1st year

  Código de colores de resistencias

  Pick four or five bands and read the value, the tolerance and the range it may measure.

• 1st year

  Resistencias en serie y en paralelo

  Up to eight resistors: the series total, the parallel total, and the current at a supply voltage.

Matemáticas del oficio

• 1st year

  Eficiencia y porcentaje

  Input and output power in watts, kilowatts or horsepower: efficiency, losses, or the input a load needs.

• 1st year

  Convertidor de longitud y área de cable

  Feet and metres, and conductor area between AWG, kcmil, circular mils and mm².

• 1st year

  Autonomía y tamaño de un banco de baterías

  Volts, amp-hours, depth of discharge and inverter efficiency: hours on a load, or the Ah a runtime needs.

Control de motores

• 4th year

  Motor control fault finder

  A hidden fault in a live ladder circuit — find it with the meter.

• 3rd year

  Ladder diagram lab

  Press the buttons and watch the rungs energise.

Power quality

• 4th year

  Calculadora de corrección del factor de potencia

  kVAR needed to go from one power factor to another, the current it saves, and the capacitance per phase.

• 4th year

  Calculadora de desbalance de tensión

  Percent unbalance from three line voltages or currents, by maximum deviation and by the negative-sequence method.

Trifásico

• 3rd year

  Calculadora de potencia trifásica

  kW, kVA, kVAR and amps from any one of them, with voltage and power factor — three-phase or single.

• 3rd year

  Conversión de impedancia delta ↔ estrella

  Turn a delta of three impedances into the equivalent wye, or back — balanced or not.

Transformers

• 3rd year

  Transformador: corriente a plena carga y relación

  Primary and secondary full-load amps, line and turns ratio, and the current in each winding for delta or wye.

• 2nd year

  Transformador monofásico

  Turns ratio and full-load primary and secondary current from the kVA and the two voltages.

Wiring

• 2nd year

  Distribución de luminarias (método de lúmenes)

  How many fixtures a room needs for a target level, from lumens, CU and light loss factor, in fc or lux.

• 2nd year

  Caída de tensión (su resistencia)

  Single- or three-phase drop from the conductor resistance you enter, in feet or metres.

Drives

• 4th year

  Calculadora de frecuencia y velocidad de un VFD

  Shaft speed at a drive frequency (or the frequency for a speed), volts-per-hertz and output voltage.

Instrumentation

• 4th year

  Calculadora de escalamiento 4–20 mA

  Loop current to process value and back, percent of span, and the voltage across a sense resistor.

Motors

• 3rd year

  Velocidad síncrona y deslizamiento de un motor

  Synchronous speed from frequency and poles, the pole count a nameplate speed implies, slip and rotor frequency.

Protection

• 4th year

  Corriente de falla de un transformador (barra infinita)

  The most short-circuit current a transformer can deliver at its terminals, from its kVA, voltage and %Z.

Services

• 4th year

  Ayuda para el cálculo de carga

  Walks the load-calculation method with every factor from your own code book: basic load, demand, extras, amps.

Ver también

• Learn by year — lessons for 1st to 4th year and journeymen
• Ejercicios de práctica
• Printable formula sheets
• Curso de control de motores